Brianna Dalesandro

Nature, Published online: 02 October 2019; doi:10.1038/s41586-019-1593-5

The authors review recent developments in our understanding of the antitumour effects of the innate immune system and how this system could be harnessed in the clinic.

Related Articles

An Activatable Chemiluminescent Probe for Sensitive Detection of γ-Glutamyl Transpeptidase Activity in vivo.

Anal Chem. 2019 Sep 27;:

Authors: An R, Wei S, Huang Z, Liu F, Ye D

Abstract
Activatable chemiluminescent probes that showed enhanced chemiluminescence upon interaction with a molecular target of interest have offered promising tools for sensing and bioimaging in terms of low background, high sensitivity and im-proved penetration depth in biological tissues. Here, we reported a γ-Glutamyl transpeptidase (GGT) activatable chemilumi-nescent probe for real-time detection of GGT activity in vitro and in living mice. The probe was designed by caging an elec-tron-withdrawing acrylic group-substituted Schaap's phenoxy-dioxetane with a GGT-recognitive substrate (γ-Glu) and a self-immolative linker (p-aminobenzyl alcohol, PABA), which was initially chemiluminescence off. Upon interaction with GGT, strong chemiluminescence with a more than 800-fold turn-on ratio could be achieved in aqueous solution, allowing to spe-cifically detect GGT activity with ultrahigh signal-to-background ratio and sensitivity in vitro and in live cells. We demon-strated that the probe was reliable to quantify the GGT in serum, permitting to accurately report the elevated levels of GGT in lipopolysaccharide (LPS)-treated mice serum. Moreover, through real-time chemiluminescence imaging of GGT activity, the designed probe was feasible to detect GGT-positive tumors in living mice after intravenous (i.v.) systemic administration. This study demonstrates the high potential of GGT-activatable chemiluminescent probe for serum assays and molecular imaging, which might find wide applications in diagnosis of GGT-related diseases.

PMID: 31560193 [PubMed - as supplied by publisher]

Millennium bug : A simple and highly efficient photosensitizer, called 4TPA‐BQ, operates by aggregation‐induced emission. A broad‐spectrum and potent antibacterial activity was attained after incubating 4TPA‐BQ with pathogens for 15 minutes. Upon lengthening of the incubation time to 12 hours, photodynamic therapy with 4TPA‐BQ targeted cancer cells and presented low toxicity to normal cells.

Abstract

Pathogen infections and cancer are two major human health problems. Herein, we report the synthesis of an organic salt photosensitizer (PS), called 4TPA‐BQ, by a one‐step reaction. 4TPA‐BQ presents aggregation‐induced emission features. Owing to the aggregation‐induced reactive oxygen species generated and a sufficiently small ΔE _ST, 4TPA‐BQ shows a satisfactorily high ¹O₂ generation efficiency of 97.8 %. In vitro and in vivo experiments confirmed that 4TPA‐BQ exhibited potent photodynamic antibacterial performance against ampicillin‐resistant Escherichia coli with good biocompatibility in a short time (15 minutes). When the incubation duration persisted long enough (12 hours), cancer cells were ablated efficiently, leaving normal cells essentially unaffected. This is the first reported time‐dependent fluorescence‐guided photodynamic therapy in one individual PS, which achieves ordered and multiple targeting simply by varying the external conditions. 4TPA‐BQ reveals new design principles for the implementation of efficient PSs in clinical applications.

Related Articles

Effects of C-terminal residues of 12-mer peptides on antibacterial efficacy and mechanism.

J Microbiol Biotechnol. 2019 Sep 18;:

Authors: Son K, Kim J, Jang M, Chauhan AK, Kim Y

Abstract
The development of new antimicrobial agents is essential for the effective treatment of diseases such as sepsis. We previously developed a new short peptide, Pap12-6, using the 12 N-terminal residues of papiliocin, which showed potent and effective antimicrobial activity against multidrug-resistant Gram-negative bacteria. Here, we investigated the antimicrobial mechanism of Pap12-6 and a newly designed peptide Pap12-7 in which the 12th Trp residue of Pap12-6 was replaced with Val to develop a potent peptide with high bacterial selectivity and different antibacterial mechanism. Both peptides showed high antimicrobial activity against Gram-negative bacteria, including multidrug-resistant Gram-negative bacteria. In addition, the two peptides showed similar anti-inflammatory activity against in lipopolysaccharide-stimulated RAW 264.7 cells, but Pap12-7 showed very low toxicities against sheep red blood cells and mammalian cells compared to that showed by Pap12-6. A calcein dye leakage assay, membrane depolarization, and confocal microscopy observations revealed that the two peptides with one single amino acid change have different mechanisms of antibacterial action: Pap12-6 directly targets the bacterial cell membrane, whereas Pap12-7 appears to penetrate the bacterial cell membrane and exert its activities in the cell. The therapeutic efficacy of Pap12-7 was further examined in a mouse model of sepsis, which increased the survival rate of septic mice. For the first time, we showed that both peptides showed anti-septic activity by reducing the infiltration of neutrophils and the production of inflammatory factors. Overall, these results indicate Pap12-7 as a novel non-toxic peptide with potent antibacterial and anti-septic activities via penetrating the cell membrane.

PMID: 31546301 [PubMed - as supplied by publisher]

Related Articles

Inactivation of the Monofunctional Peptidoglycan Glycosyltransferase SgtB Allows Staphylococcus aureus To Survive in the Absence of Lipoteichoic Acid.

J Bacteriol. 2019 01 01;201(1):

Authors: Karinou E, Schuster CF, Pazos M, Vollmer W, Gründling A

Abstract
The cell wall of Staphylococcus aureus is composed of peptidoglycan and the anionic polymers lipoteichoic acid (LTA) and wall teichoic acid. LTA is required for growth and normal cell morphology in S. aureus Strains lacking LTA are usually viable only when grown under osmotically stabilizing conditions or after the acquisition of compensatory mutations. LTA-negative suppressor strains with inactivating mutations in gdpP, which resulted in increased intracellular c-di-AMP levels, were described previously. Here, we sought to identify factors other than c-di-AMP that allow S. aureus to survive without LTA. LTA-negative strains able to grow in unsupplemented medium were obtained and found to contain mutations in sgtB, mazE, clpX, or vraT The growth improvement through mutations in mazE and sgtB was confirmed by complementation analysis. We also showed that an S. aureus sgtB transposon mutant, with the monofunctional peptidoglycan glycosyltransferase SgtB inactivated, displayed a 4-fold increase in the MIC of oxacillin, suggesting that alterations in the peptidoglycan structure could help bacteria compensate for the lack of LTA. Muropeptide analysis of peptidoglycans isolated from a wild-type strain and sgtB mutant strain did not reveal any sizable alterations in the peptidoglycan structure. In contrast, the peptidoglycan isolated from an LTA-negative ltaS mutant strain showed a significant reduction in the fraction of highly cross-linked peptidoglycan, which was partially rescued in the sgtB ltaS double mutant suppressor strain. Taken together, these data point toward an important function of LTA in cell wall integrity through its necessity for proper peptidoglycan assembly.IMPORTANCE The bacterial cell wall acts as a primary defense against environmental insults such as changes in osmolarity. It is also a vulnerable structure, as defects in its synthesis can lead to growth arrest or cell death. The important human pathogen Staphylococcus aureus has a typical Gram-positive cell wall, which consists of peptidoglycan and the anionic polymers LTA and wall teichoic acid. Several clinically relevant antibiotics inhibit the synthesis of peptidoglycan; therefore, it and teichoic acids are considered attractive targets for the development of new antimicrobials. We show that LTA is required for efficient peptidoglycan cross-linking in S. aureus and inactivation of a peptidoglycan glycosyltransferase can partially rescue this defect, together revealing an intimate link between peptidoglycan and LTA synthesis.

PMID: 30322854 [PubMed - indexed for MEDLINE]

Related Articles

Structure and function of lipid A-modifying enzymes.

Ann N Y Acad Sci. 2019 Sep 25;:

Authors: Anandan A, Vrielink A

Abstract
Lipopolysaccharides are complex molecules found in the cell envelop of many Gram-negative bacteria. The toxic activity of these molecules has led to the terminology of endotoxins. They provide bacteria with structural integrity and protection from external environmental conditions, and they interact with host signaling receptors to induce host immune responses. Bacteria have evolved enzymes that act to modify lipopolysaccharides, particularly the lipid A region of the molecule, to enable the circumvention of host immune system responses. These modifications include changes to lipopolysaccharide by the addition of positively charged sugars, such as N-Ara4N, and phosphoethanolamine (pEtN). Other modifications include hydroxylation, acylation, and deacylation of fatty acyl chains. We review the two-component regulatory mechanisms for enzymes that carry out these modifications and provide details of the structures of four enzymes (PagP, PagL, pEtN transferases, and ArnT) that modify the lipid A portion of lipopolysaccharides. We focus largely on the three-dimensional structures of these enzymes, which provide an understanding of how their substrate binding and catalytic activities are mediated. A structure-function-based understanding of these enzymes provides a platform for the development of novel therapeutics to treat antibiotic resistance.

PMID: 31553069 [PubMed - as supplied by publisher]

Mighty macrocycles: an in‐depth look at the binding parameters of teixobactin, a macrocyclic antimicrobial peptide, with its membrane target, lipid II. Teixobactin binds to analogues of both Gram‐positive and Gram‐negative bacterial lipids, allowing its activity scope to be extended to both types of organisms using membrane‐disrupting peptides.

Abstract

The prevalence of life‐threatening, drug‐resistant microbial infections has challenged researchers to consider alternatives to currently available antibiotics. Teixobactin is a recently discovered “resistance‐proof” antimicrobial peptide that targets the bacterial cell wall precursor lipid II. In doing so, teixobactin exhibits potent antimicrobial activity against a wide range of Gram‐positive organisms. Herein we demonstrate that teixobactin and several structural analogues are capable of binding lipid II from both Gram‐positive and Gram‐negative bacteria. Furthermore, we show that when combined with known outer membrane‐disrupting peptides, teixobactin is active against Gram‐negative organisms.

One of the WHO's three critical priority pathogens, Acinetobacter baumannii, for which new antibiotics are urgently needed is one step closer to being tackled, as researchers from the Department of Chemistry—University of Warwick have made a breakthrough in understanding the enzymes that assemble the antibiotic enacyloxin.

The novel small molecules, based on new target, new chemical structure and new antimicrobial mechanism, are different from those of existing antibiotics. The new drug candidates demonstrate much effective abilities of inhibiting bacterial growth than commonly used antibiotics, yet with no toxicity to human cells.

Nature Microbiology, Published online: 20 September 2019; doi:10.1038/s41564-019-0561-z

Since the emergence of methicillin-resistant Staphylococcus aureus 60 years ago, scientists have been trying to engineer β-lactam antibiotics to restore drug susceptibility. Genomic data now shows that clavulanic acid (a β-lactamase inhibitor) can restore susceptibility in many strains, but only if they carry key mutations.

Related Articles

l-Rhamnosylation of wall teichoic acids promotes efficient surface association of Listeria monocytogenes virulence factors InlB and Ami through interaction with GW domains.

Environ Microbiol. 2018 11;20(11):3941-3951

Authors: Carvalho F, Sousa S, Cabanes D

Abstract
Wall teichoic acids (WTAs) are important surface glycopolymers involved in various physiological processes occurring in the Gram-positive cell envelope. We previously showed that the decoration of Listeria monocytogenes (Lm) WTAs with l-rhamnose conferred resistance against antimicrobial peptides. Here, we show that WTA l-rhamnosylation also contributes to physiological levels of autolysis in Lm through a mechanism that requires efficient association of Ami, a virulence-promoting autolysin belonging to the GW protein family, to the bacterial cell surface. Importantly, WTA l-rhamnosylation also controls the surface association of another GW protein, the invasin internalin B (InlB), that promotes Lm invasion of host cells. Whereas WTA N-acetylglucosaminylation is not a prerequisite for GW protein surface association, lipoteichoic acids appear to also play a role in the surface anchoring of InlB. Strikingly, while the GW domains of Ami, InlB and Auto (another autolysin contributing to cell invasion and virulence) are sufficient to mediate surface association, this is not the case for the GW domains of the remaining six uncharacterized Lm GW proteins. Overall, we reveal WTA l-rhamnosylation as a bacterial surface modification mechanism that contributes to Lm physiology and pathogenesis by controlling the surface association of GW proteins involved in autolysis and infection.

PMID: 29984543 [PubMed - indexed for MEDLINE]

Related Articles

Vitamin A Enhances Macrophages Activity Against B16-F10 Malignant Melanocytes: A New Player for Cancer Immunotherapy?

Medicina (Kaunas). 2019 Sep 18;55(9):

Authors: Oliveira S, Costa J, Faria I, Guerreiro SG, Fernandes R

Abstract
Background and objectives: The incidence of cutaneous melanoma has been increasing. Melanoma is an aggressive form of skin cancer irresponsive to radiation and chemotherapy, rendering this cancer a disease with poor prognosis: In order to surpass some of the limitations addressed to melanoma treatment, alternatives like vitamins have been investigated. In the present study, we address this relationship and investigate the possible role of vitamin A. Materials and Methods: We perform a co-culture assay using a macrophage cell model and RAW 264.7 from mouse, and also a murine melanoma cell line B16-F10. Macrophages were stimulated with both Escherichia coli lipopolysaccharides (LPS) as control, and also with LPS plus vitamin A. Results: Using B16-F10 and RAW 264.7 cell lines, we were able to demonstrate that low concentrations of vitamin A increase cytotoxic activity of macrophages, whereas higher concentrations have the opposite effect. Conclusion: These findings can constitute a new point of view related to immunostimulation by nutrients, which may be considered one major preventive strategy by enhancing the natural defense system of the body.

PMID: 31540438 [PubMed - in process]

Related Articles

PROTAC Degradation of IRAK4 for the Treatment of Neurodegenerative and Cardiovascular Diseases.

ACS Med Chem Lett. 2019 Sep 12;10(9):1251-1252

Authors: Kargbo RB

PMID: 31531192 [PubMed]

A deadly, antibiotic-resistant bacterium can be sterilized by hijacking its heme-acquisition system, which is essential for its survival. The new strategy, developed by Nagoya University researchers and colleagues in Japan, was published in the journal ACS Chemical Biology.

Nature, Published online: 18 September 2019; doi:10.1038/d41586-019-02754-7

Adoption of molecular tests for influenza has been slow — partly because of their high cost.

An interdisciplinary team of researchers at the Hong Kong University of Science and Technology (HKUST) unraveled how a toxin released by Escherichia coli (E. coli) – a human gut bacteria, is connected to colorectal cancer, offering new insights to the health impact of this prevalent bacteria and facilitating future research on the prevention of this third most common cancer worldwide.

Related Articles

Development of an In Situ Cancer Vaccine via Combinational Radiation and Bacterial-Membrane-Coated Nanoparticles.

Adv Mater. 2019 Sep 16;:e1902626

Authors: Patel RB, Ye M, Carlson PM, Jaquish A, Zangl L, Ma B, Wang Y, Arthur I, Xie R, Brown RJ, Wang X, Sriramaneni R, Kim K, Gong S, Morris ZS

Abstract
Neoantigens induced by random mutations and specific to an individual's cancer are the most important tumor antigens recognized by T cells. Among immunologically "cold" tumors, limited recognition of tumor neoantigens results in the absence of a de novo antitumor immune response. These "cold" tumors present a clinical challenge as they are poorly responsive to most immunotherapies, including immune checkpoint inhibitors (ICIs). Radiation therapy (RT) can enhance immune recognition of "cold" tumors, resulting in a more diversified antitumor T-cell response, yet RT alone rarely results in a systemic antitumor immune response. Therefore, a multifunctional bacterial membrane-coated nanoparticle (BNP) composed of an immune activating PC7A/CpG polyplex core coated with bacterial membrane and imide groups to enhance antigen retrieval is developed. This BNP can capture cancer neoantigens following RT, enhance their uptake in dendritic cells (DCs), and facilitate their cross presentation to stimulate an antitumor T-cell response. In mice bearing syngeneic melanoma or neuroblastoma, treatment with BNP+RT results in activation of DCs and effector T cells, marked tumor regression, and tumor-specific antitumor immune memory. This BNP facilitates in situ immune recognition of a radiated tumor, enabling a novel personalized approach to cancer immunotherapy using off-the-shelf therapeutics.

PMID: 31523868 [PubMed - as supplied by publisher]

Related Articles

Exposure of Staphylococcus aureus to Targocil Blocks Translocation of the Major Autolysin Atl across the Membrane, Resulting in a Significant Decrease in Autolysis.

Antimicrob Agents Chemother. 2018 07;62(7):

Authors: Tiwari KB, Gatto C, Walker S, Wilkinson BJ

Abstract
Peptidoglycan (PG) and wall teichoic acid (WTA) are the major staphylococcal cell wall components, and WTA biosynthesis has recently been explored for drug development. Targocil is a novel agent that targets the TarG subunit of the WTA translocase (TarGH) that transports WTA across the membrane to the wall. Previously we showed that targocil treatment of a methicillin-susceptible Staphylococcus aureus strain led to a rapid shut down of cellular autolysis. Targocil II, which targets the TarH subunit of TarGH, also resulted in a drastic decrease in autolysis. Here, we address the mechanism of targocil-mediated decreased autolysis. The mechanism is WTA dependent since targocil treatment decreased autolysis in methicillin-resistant strains but not in a WTA-deficient mutant. Similar to cellular autolysis, autolysin-retaining crude cell walls isolated from targocil-treated cells had vastly decreased autolytic activity compared to those from untreated cells. Purified cell walls from control and targocil-treated cells, which lack autolytic activity, were similarly susceptible to lysozyme and lysostaphin and had similar O-acetyl contents, indicating that targocil treatment did not grossly alter PG structure and chemistry. Purified cell walls from targocil-treated cells were highly susceptible to autolysin extracts, supporting the notion that targocil treatment led to decreased autolysin in the crude cell walls. Quantitative real-time PCR analysis revealed that the decrease in autolysis in the targocil-exposed cells was not due to transcriptional repression of the autolysin genes atl, lytM, lytN, and sle1 Zymographic analysis of peptidoglycan hydrolase profiles showed a deficiency of cell surface autolysins in targocil-treated cells but higher activity in cell membrane fractions. Here, we propose that the untranslocated WTA molecules in the targocil-exposed cells sequester Atl at the membrane, resulting in significantly decreased autolysis.

PMID: 29735561 [PubMed - indexed for MEDLINE]

Related Articles

Sortase-Dependent Proteins Promote Gastrointestinal Colonization by Enterococci.

Infect Immun. 2019 03;87(5):

Authors: Banla LI, Pickrum AM, Hayward M, Kristich CJ, Salzman NH

Abstract
The human gastrointestinal tract (GIT) is inhabited by a dense microbial community of symbionts. Enterococci are among the earliest members of this community and remain core members of the GIT microbiota throughout life. Enterococci have also recently emerged as opportunistic pathogens and major causes of nosocomial infections. Although recognized as a prerequisite for infection, colonization of the GIT by enterococci remains poorly understood. One way that bacteria adapt to dynamic ecosystems like the GIT is through the use of their surface proteins to sense and interact with components of their immediate environment. In Gram-positive bacteria, a subset of surface proteins relies on an enzyme called sortase for covalent attachment to the cell wall. Here, we show that the housekeeping sortase A (SrtA) enzyme promotes intestinal colonization by enterococci. Furthermore, we show that the enzymatic activity of SrtA is key to the ability of Enterococcus faecalis to bind mucin (a major component of the GIT mucus). We also report the GIT colonization phenotypes of E. faecalis mutants lacking selected sortase-dependent proteins (SDPs). Further examination of the mucin binding ability of these mutants suggests that adhesion to mucin contributes to intestinal colonization by E. faecalis.

PMID: 30804098 [PubMed - indexed for MEDLINE]

Related Articles

DL-endopeptidases function as both cell wall hydrolases and poly-γ-glutamic acid hydrolases.

Microbiology. 2018 03;164(3):277-286

Authors: Fukushima T, Uchida N, Ide M, Kodama T, Sekiguchi J

Abstract
Biopolymers on the cell surface are very important for protecting microorganisms from environmental stresses, as well as storing nutrients and minerals. Synthesis of biopolymers is well studied, while studies on the modification and degradation processes of biopolymers are limited. One of these biopolymers, poly-γ-glutamic acid (γ-PGA), is produced by Bacillus species. Bacillus subtilis PgdS, possessing three NlpC/P60 domains, hydrolyses γ-PGA. Here, we have demonstrated that several dl-endopeptidases with an NlpC/P60 domain (LytE, LytF, CwlS, CwlO, and CwlT) in B. subtilis digest not only an amide bond of d-γ-glutamyl-diaminopimelic acid in peptidoglycans but also linkages of γ-PGA produced by B. subtilis. The hydrolase activity of dl-endopeptidases towards γ-PGA was inhibited by IseA, which also inhibits their hydrolase activity towards peptidoglycans, while the hydrolysis of PgdS towards γ-PGA was not inhibited. PgdS hydrolysed only the d-/l-Glu‒d-Glu linkages of d-Glu-rich γ-PGA (d-Glu:l-Glu=7 : 3) and l-Glu-rich γ-PGA (d-Glu:l-Glu=1 : 9), indicating that PgdS can hydrolyse only restricted substrates. On the other hand, the dl-endopeptidases in B. subtilis cleaved d-/l-Glu‒d-/l-Glu linkages of d-Glu-rich γ-PGA (d-Glu:l-Glu=7 : 3), indicating that these enzymes show different substrate specificities. Thus, the dl-endopeptidases digest γ-PGA more flexibly than PgdS, even though they are annotated as "dl-endopeptidase, digesting the d-γ-glutamyl-diaminopimelic acid linkage (d‒l amino acid bond)".

PMID: 29458655 [PubMed - indexed for MEDLINE]

by Camilla Jensen, Kristoffer T. Bæk, Clement Gallay, Ida Thalsø-Madsen, Lijuan Xu, Ambre Jousselin, Fernando Ruiz Torrubia, Wilhelm Paulander, Ana R. Pereira, Jan-Willem Veening, Mariana G. Pinho, Dorte Frees

β-lactam antibiotics interfere with cross-linking of the bacterial cell wall, but the killing mechanism of this important class of antibiotics is not fully understood. Serendipitously we found that sub-lethal doses of β-lactams rescue growth and prevent spontaneous lysis of Staphylococcus aureus mutants lacking the widely conserved chaperone ClpX, and we reasoned that a better understanding of the clpX phenotypes could provide novel insights into the downstream effects of β-lactam binding to the PBP targets. Super-resolution imaging revealed that clpX cells display aberrant septum synthesis, and initiate daughter cell separation prior to septum completion at 30°C, but not at 37°C, demonstrating that ClpX becomes critical for coordinating the S. aureus cell cycle as the temperature decreases. FtsZ localization and dynamics were not affected in the absence of ClpX, suggesting that ClpX affects septum formation and autolytic activation downstream of Z-ring formation. Interestingly, oxacillin antagonized the septum progression defects of clpX cells and prevented lysis of prematurely splitting clpX cells. Strikingly, inhibitors of wall teichoic acid (WTA) biosynthesis that work synergistically with β-lactams to kill MRSA synthesis also rescued growth of the clpX mutant, as did genetic inactivation of the gene encoding the septal autolysin, Sle1. Taken together, our data support a model in which Sle1 causes premature splitting and lysis of clpX daughter cells unless Sle1-dependent lysis is antagonized by β-lactams or by inhibiting an early step in WTA biosynthesis. The finding that β-lactams and inhibitors of WTA biosynthesis specifically prevent lysis of a mutant with dysregulated autolytic activity lends support to the idea that PBPs and WTA biosynthesis play an important role in coordinating cell division with autolytic splitting of daughter cells, and that β-lactams do not kill S. aureus simply by weakening the cell wall.

Related Articles

The involvement of McpB chemoreceptor from Pseudomonas aeruginosa PAO1 in virulence.

Sci Rep. 2019 Sep 11;9(1):13166

Authors: García-Fontana C, Vílchez JI, González-Requena M, González-López J, Krell T, Matilla MA, Manzanera M

Abstract
Pseudomonas aeruginosa is an opportunistic human pathogen causing infections in a variety of plant and animal hosts. The gene mcpB, part of the chemosensory gene cluster II, encodes a soluble chemoreceptor whose function remains unknown. Previous studies show that the cheB2 gene, also located in the chemosensory cluster II, is involved in a specific response during infection and it is required for full pathogenicity of P. aeruginosa. To determine whether the McpB (or Aer2) chemoreceptor is involved in virulence processes, we generated a mcpB mutant and tested its phenotype using a virulence-measuring system. This system was developed by our group and is based on different bioassays using organisms living at different soil trophic levels, including microbial, nematode, arthropod, annelid, and plant model systems. The deletion of mcpB resulted in an attenuation of bacterial virulence in different infection models, and wild-type virulence was restored following genetic complementation of the mutant strain. Our study indicates that the McpB chemoreceptor is linked to virulence processes and may constitute the basis for the development of alternative strategies against this pathogen.

PMID: 31511598 [PubMed - in process]

Biopharmaceutics consisting of middle molecules, for example, peptide or nucleic-acid aptamers, have been attracting attention as promising molecular modalities in current drug discovery.

Related Articles

Two c-type lectins from Venerupis philippinarum: Possible roles in immune recognition and opsonization.

Fish Shellfish Immunol. 2019 Sep 06;:

Authors: Zhang J, Zhang Y, Chen L, Yang J, Wei Q, Yang B, Liu X, Yang D

Abstract
In the study, two c-type lectins were identified and characterized from the manila clam Venerupis philippinarum (designed as VpClec-1 and VpClec-2, respectively). Multiple alignments and phylogenetic analysis strongly suggested that they were new members of the c-type lectin superfamily. In normal tissue of clams, both VpClec-1 and VpClec-2 transcripts were highly expressed in the tissue of hepatopancreas. After Vibrio anguillarum challenge, the temporal expression of both VpClec-1 and VpClec-2 transcripts was up-regulated in the hemocytes of manila clams. The recombinant protein VpClec-1 (rVpClec-1) showed obvious binding activities to lipopolysaccharide (LPS), peptidoglycan (PGN), glucan and zymosan in vitro, while the recombinant protein VpClec-2 (rVpClec-2) could only bind LPS, glucan and zymosan. Coinciding with the PAMPs binding assay, both rVpClec-1 and rVpClec-2 displayed broad agglutination and antibacterial activities towards Vibrio harveyi, Vibrio splendidus, Vibrio anguillarum, Enterobacter cloacae and Aeromonas hydrophila. Moreover, the phagocytosis and encapsulation ability of hemocytes could be significantly enhanced by rVpClec-1 and rVpClec-2. Notably, the rVpClec-1 but not rVpClec-2 elicited a chemotactic response from hemocytes. All the results showed that VpClec-1 and VpClec-2 functioned as pattern recognition receptors (PRRs) with distinct recognition spectrum, and involved in the innate immune responses of manila clams.

PMID: 31499201 [PubMed - as supplied by publisher]

Related Articles

L,D-transpeptidase Specific Probe Reveals Spatial Activity of Peptidoglycan Crosslinking.

ACS Chem Biol. 2019 Sep 05;:

Authors: Pidgeon SE, Apostolos AJ, Nelson JM, Shaku M, Rimal B, Islam MN, Crick DC, Kim SJ, Pavelka MS, Kana BD, Pires MM

Abstract
Peptidoglycan (PG) is a crosslinked, mesh-like scaffold endowed with the strength to withstand the internal pressure of bacteria. Crosslinking of peptide chains within PG is an essential process and its disruption thereof underpins the potency of several classes of antibiotics. Two primary crosslinking modes have been identified that are carried out by D,D-transpeptidases and L,D-transpeptidases (Ldts). The nascent PG from each enzymatic class is structurally unique, which results in different crosslinking configurations. Recent advances in PG cellular probes have been powerful in advancing the understanding of D,D-transpeptidation by Penicillin Binding Proteins (PBPs). In contrast, no cellular probes have been previously described to directly interrogate Ldt function in live cells. Herein, we describe a new class of Ldt-specific probes composed of structural analogs of nascent PG, which are metabolically incorporated into the PG scaffold by Ldts. With a panel of tetra-peptide PG stem mimics, we demonstrated that subtle modifications such as amidation of iso-Glu can control PG crosslinking. Ldt-probes were applied to quantify and track the localization of Ldt activity in Enterococcus faecium, Mycobacterium smegmatis, and Mycobacterium tuberculosis. These results confirm that our Ldt probes are specific and suggest that the primary sequence of the stem peptide can control Ldt crosslinking levels. We anticipate that unraveling the interplay between Ldts and other crosslinking modalities may reveal the organization of the PG structure in relation to the spatial localization of crosslinking machineries.

PMID: 31487148 [PubMed - as supplied by publisher]

Nature, Published online: 04 September 2019; doi:10.1038/s41586-019-1521-8

The re-seeding of antibiotic-resistant persister subpopulations of Salmonella enterica into the gut lumen favours the transfer of resistance plasmids to gut-resident enterobacteria, showing that even small reservoirs of persister bacteria facilitate the spread of antibiotic resistance.